In Oz after a pilot of IFR reports visual we may for sequencing/traffic management descend them below the Lowest Safe Altitude, we would say something like "Descend to 3 thousand, Visual" i.e. don't run yourself into a tree/hill but keep going down to 3 thousand at your discretion/judgement... This may help us get a shorter downwind/closer intercept of final or the like, less track miles etc...
I would guess this is just a way of getting below the Radar Lowest Safe or Minimum Safe Altitude, before issuing the clearance for final, a way of 'expediting the traffic'.